Ben Carson

Jeb Bush

Jeb Bush told Trump, "Donald you're not going to be able to insult your way to the presidency."

Credit: John Locher/AP

John Kasich

Ohio Gov. John Kasich speaks during the Republican debate in Las Vegas.

Credit: Justin Sullivan/Getty Images

Rand Paul

Rand Paul criticized Trump's proposal to kill the families of terror suspects: "If you're going to support Donald Trump are you going to get rid of the Constitution?"

Credit: John Locher/AP

Chris Christie

New Jersey Gov. Chris called President Barack Obama a "feckless weakling."

Credit: John Locher/AP

Sen. Ted Cruz (R-TX) (R) speaks as Donald Trump listens in Las Vegas.

Credit: Justin Sullivan/Getty Images

Republican debate

(L-R) Dr. Ben Carson, businessman Donald Trump and Sen. Ted Cruz hold their hands over their hearts for the singing of the U.S. national anthem before the start of the Republican presidential debate in Las Vegas.

George Pataki

Former New York Gov. George Pataki delivers his opening statement during a forum for lower polling candidates held prior to the Republican presidential debate in Las Vegas.

Pataki praised the former New York Police Department program of monitoring mosques.

Credit: Mike Blake/Reuters

George Pataki & Mike Huckabee

Former Gov. George Pataki (L) and former Gov. Mike Huckabee (C) talk with debate moderator and Salem Radio Network talk show host Hugh Hewitt (R) during a commercial break during the Republican presidential debate in Las Vegas.

Credit: Mike Blake/Reuters

Lindsey Graham

Sen. Lindsey Graham has his tie straightened by a debate staff member during a commercial break in the midst of a forum for lower polling candidates held before the main Republican presidential debate in Las Vegas.

Credit: Mike Blake/Reuters

Republican debate

General view of the venue as CNN's Wolf Blitzer (L) moderates as former New York Gov. George Pataki, former Arkansas Gov. Mike Huckabee, former Pennsylvania Sen. Rick Santorum and South Carolina Sen. Lindsey Graham (L to R) participate in a forum for lower polling candidates held before the Republican presidential debate in Las Vegas, Nevada December 15, 2015.

Republican debate

Republican debate

Highlights of the last Republican debate of the year, with Sen. Ted Cruz (R-TX) gaining in the polls in Iowa and other early voting states and Donald Trump rising in national polls, Dec. 15, 2015.

Former New York Gov. George Pataki, former Arkansas Gov. Mike Huckabee, former Pennsylvania Sen. Rick Santorum and South Carolina Sen. Lindsey Graham (L to R) pose before participating in a forum for lower polling candidates held before the main Republican presidential debate in Las Vegas, Dec. 15, 2015.

Credit: Mike Blake/Reuters

Republican debate

Former Gov. George Pataki, former Gov. Mike Huckabee, former Sen. Rick Santorum and Sen. Lindsey Graham (R-SC) stand on stage before during the Republican presidential debate in Las Vegas.